In my system there was a check valve in the feed line about 10" from the intake, then another one real close to the solenoid, those were the only ones i have. And yes, i was not LOLing when that box popped, cause at that time i had no idea that box even existed, then i tried to fix it with expoxy plastic weld, that didnt work, so i dropped $40 for a new one from the stealership. I just blow through mine to check them, or if you have a vacuum guage you can just apply vacuum to each side and you should have one side that hold vacuum, but even if the vacuum is leaking through the check valve a little, i would replace it.

Thanks again Camaro,

By the way, have you seen any MPG improvement with the EDGE computer?
I heard they do wonders with Diesel, not so with Gas. What are the facts? Important at these gas prices.

Ah, not too much MPG improvement with the Edge, when i was considering it i wasnt looking for better MPG, i was looking for something that would wake up my 4.6 and it definately did, and definately worth the money in my opinion. i really dont mess with anything in the Edge, i just use a stock #2 tune, works great for me!

Great thread XJ. One question I had was, if I just rig it temporarily and put a screw in the vacuum line to get around, will the 4WD selector switch still properly work the transfer case on the fly..without damaging anything? Following the original post from the beginning, as I understand it, the only detriment would be spinning the hubs/axles full time will cost a little less gas mileage, but nothing else? The function would still be the same whether in 2H, 4H, or 4L?

gregster, in theory, yes. That said, one thing this thread has not mentioned is the 4X4 capability was not intended for full-time hard surface use. Although the transfer case will only engage / disengage based the selector switch, each front wheel still spins at a different rate from the other (i.e. inside wheel spins slower than the outside wheel in a turn). I don't know if the front differential allows for 'slip' with the hubs engaged and if not, you could be looking at further damage to the axle, IWEs or differential.

It is my opinion that the front does allow slip, as before i looked at my setup, im guessing i drove around over a year with everything engaged in the front end (but not the transfer case). And still to this day no front differential problems because of it.

So yes, you can plug a line and let the IWEs stay engaged without damage. And 4WD will still work correctly when you turn the selector. Because when you turn the selector two things happen, the IWE solenoid releases vacuum and engage the IWEs to the front axles, and then the transfer case engages. Well you are half way there already by having the IWEs engaged to the axles.

The line i would plug would be the main IWE system line that comes off the intake. There should be a check valve or some sort of connection not too far from the intake where you can seperate the line and plug the side coming from the intake. And you will be fine until you get to fixing it.

Thanks guys. I definitely hope not to attempt using 4wd full time on the street, but knowing me, if I plug the vacuum line and get used to it, 6 months down the road when I need 4wd, and instinctively go for the switch, just wanted to make sure my transfer case doesn't grenade.

I'm really glad I got on this thread. I heard that "wheel of fortune"sound vaguely at first a while ago, and infrequently, and had found xj's description. It then became more progressive. It started happening about every 60 seconds, and I would stop it by briefly selecting 4H. I happened to be driving by the dealer (or should I say squealor) when it got real bad, so I pulled in. They said both IWE's were clicking and bad, and quoted $1350. Didn't mention the solenoid. Having read the decription, I believe it highly unlikely they both go bad the same instant. Sounds like a loss of vacuum somewhere in the solenoid, lines or maybe one of the IWE's. Their explanation doesn't seem plausible. I'll start with the solenoid first for $40, then progress to and test the other items. At the end of the day, maybe both the IWE's do need to go, but I'll go a piee at a time, and I suspect it probably wont cost $1350?

First off, I'd like to give props to xjcamaro for starting this thread and still responding to people's questions almost 2-1/2 years after the initial post ... that's awesome. I didn't think I'd be able to contribute to this thread but after reading all 15 pages I find that I do have something to add.

So last week I got the dreaded rattle. I thought it was the transfer case so I took it to the dealer and had them take a look at it and flush my transfer case and both differentials since I just hit 100k. They tell me the rattle is the worn out isolator on the dual exhaust (luckily they don't charge me for this wrong diagnosis). I go home, change the isolator and then find this post after my truck still makes the rattle. I followed xjcamaro's instructions (To-The-T) and find out I have a leak somewhere past the solenoid in the vacuum lines traveling between the actuators on the two front wheels.

Next I go back to Ford to see how much the new line would cost and how much it'd be to replace it. It's $75 for the hose system (they coulda knocked the price down to $68 for me...woohoo) and around $200 to install. Luckily an old mechanic comes out of the shop and says he knows exactly what's wrong and tells me exactly what to look for. Thank God for that mechanic cause he just saved me darn near $300.

This is my contribution to this thread ... The mechanic tells me these lines have a tendency to wear out in two locations: 1) behind the battery where some vehicles drop battery acid on the line 2) where the hose bends under the right front wheel well fender and splits to go to each wheel.

In addition to getting this helpful bit of information, I also got the vacuum line diagram from the dealer and the mechanic pointed out the ever so helpful splice disconnect in the front of the truck behind the front crossmember.

So I come home, take my truck back apart, and uncouple the disconnect behind the front crossmember so I can check the right and left sides independently. This is where I nailed the leak down to the front right side. I then pulled the line all the way down from the solenoid out below the wheel well fender. This is where I found the extremely brittle bend in the plastic line. I patched the line using some fuel line from my local hardware store and the truck is all fixed. I checked both actuators to make sure they were operating correctly before putting the wheels on and taking her for a test drive. After driving her around town .... no more rattle. Thank You XJCamaro and Leonard (the old man mechanic from Ford). I'm starting to think whenever you take your truck to the dealer for service ... request the oldest, most experienced man there cause chances are they've seen these problems before.

So what anyone experiencing this problem for the first time should take out of this post is this: 1) if it's the line leaking, check the two problem areas before thinking about replacing the entire line. 2) the front disconnect behind the front cross member is very helpful in pinpointing the leak from either the right or left side. (just crawl under your truck right in the middle and look up behind the cross member. You can't miss it)

I have posted a few pictures of the disconnect, my fix on the bend, and the vacuum line diagram I got from the Dealer. You can find them in my photos.

fGlad you got it fixed! And thanks for adding some more diagnosing information! I think that will help people out there. I didnt even bother looking at the lines when i originally had the problem, i just ran all new lines of my own using general vacuum line, i figured it would be just as fast if not faster than pulling out and looking for cracks in the originals, but im glad your trouble spot was easy to find.

Very helpful thread thank you very much. Im having some issues and believe I have it nailed down. One question I have is if the truck will shift into 4low easily does that mean the transfer case shift motor is working properly?

Thanks to everyone for posts. Took truck to dealer for diagnosis and said I needed a new solenoid. Got one and had them install it, good thing they installed it because they had to reprogram system. Have not had any problems since then, should knock on wood.
Somebody mentioned leaving front hubs engaged, if you have stock differential it should be an open differential and the front wheels should spin in turns at diffrent speed without problems.

So, I have the same problem, but the only difference is when I hit a bump I get a clunking. I have it in 4wd now to stop the grinding until i can get some time to drop it off to get it fixed, any rough estimates on what it might cast me? I'm not good at working on cars at all.

So, I have the same problem, but the only difference is when I hit a bump I get a clunking. I have it in 4wd now to stop the grinding until i can get some time to drop it off to get it fixed, any rough estimates on what it might cast me? I'm not good at working on cars at all.

You'd be better off yanking the lines from the IWEs rather than driving around in 4wd. Could cause more damage than needed. Whereas pulling the pressure out of the system will also stop the grinding which is the IWEs trying to engage.

The solenoid is on the firewall on the passenger side just below the drip rail. Take the vacuum pressure out of the system and the hubs will engage without the transfer case being engaged. Basically you have a leak somewhere in the system now and that's causing the partial engage.

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